The present invention relates to a method for ascertaining or determining the temperature in an electrical battery.
Knowledge of the battery temperature is often required for monitoring and/or controlling a battery, for example to establish the charging voltage in dependence on the battery temperature or to ascertain the state of charge as accurately as possible. In this respect there is the problem that, for various reasons, there is no temperature sensor installed in the battery or a temperature sensor cannot be installed in the battery. This causes increased costs to be incurred, for example by providing an additional temperature sensor. Moreover, additional cabling is required at the battery, in order to connect the temperature sensor integrated in the battery to an evaluation unit.
It is therefore proposed in DE 198 06 135 A1 to calculate the temperature of a battery in a vehicle electrical system in dependence on at least two temperatures measured outside the battery on the basis of a thermal model. In this case, allowance is to be made at least for the engine temperature and the ambient temperature.
Furthermore, U.S. Pat. No. 5,079,716 discloses a method for determining the battery temperature by addition of a previously ascertained battery temperature value to the product of the average vehicle speed and the sum of a number of temperature values measured in the vicinity of the battery.
U.S. Pat. No. 5,711,605 describes a method for predicting the battery temperature by determining the air temperature in the vicinity and heat transfer coefficients in conjunction with empirical factors.
DE 101 31 259 A1 also proposes a method for ascertaining a battery temperature in dependence on various temperatures, in particular the engine temperature and the ambient temperature, making allowance for a further temperature of a control device arranged in the immediate vicinity of the battery and the operating state of the control device.
U.S. Pat. No. 4,342,963 describes an automated battery tester which compensates for the influence of the temperature of the electrolyte, in that a connecting part that is provided for the connection to the battery contains a temperature sensor, and the test conditions are changed in dependence on the two measured temperature values obtained before and after connection of the connecting part to the battery.
DE 102 08 651 A1 discloses a method for ascertaining the state of charge of a battery in dependence on a temperature difference which is determined from a thermal balance. The measured temperatures are internal temperatures of the battery and the thermal balance relates to internal processes of the battery.
DE 101 34 065 A1 describes a method for predicting the electrical load capacity of a storage battery, in which allowance is made for the thermal effects associated with the current flow through the battery. In this case, an adjustment takes place between the ambient temperature and the battery temperature. The thermal balance makes allowance for the Joulean heat caused by the battery being heated up by the flow of current and a reversible heating output.
It would be desirable to provide an improved method and an improved device for ascertaining the temperature in an electrical battery by measuring at least one temperature value at a respective temperature measuring point outside the battery in the vicinity of the battery, in order to be able to determine the battery temperature still more accurately.